by bending rolled or'drawn sections. However, in the case of elbows having a short radius this practice is impracticable because the portion of the pipe on the inside of the bend will buckle and the wall on the outside or the bend will stretch, thereby reducing the thickness of the metal and rendering imminent the possibility of rupture.

Accordingly, a primary ob ect of the present invention is to depa-rtfrom the practice above indicated and provide curved tubular sections by a welding method. In that way the sections may be made of rolled steel wit its consequent advantages not only from an economical stand oint, but also provide 0 curved sections 0? increased strength and durability.

Any convenient and practical form o f apparatus may be used to carry the method into efiect but by way of illustrating the novel 5 steps of the method involved herein reference may be made to the accompanymg drawings, in which 1 t Figure 1 illustrates perspective views of.

a pair of blanks arranged to form the curved section. 1

Figure 2 is a perspective view of the flat rectangular strips of Fig. 1 curved transversely in accordance with the second step 5 of the invention.

' Figure 3 shows the pipe sections of Fig. 2

curved longitudinally and ready for matched 1 assembly.

60 elbow, the sections being welded together.

been

Figure 5 is an end elevation of the completed elbow shown in Fig. 4.

Figures 6, 7 and 8 are detail side elevatlons respectively of 30, and 180 hol- 1 low sectionsmade in accordance with the 'present invention.

Similar reference characters designate corresp onding parts throughout the several figures ofthe drawings.

In carrying the invention into effect it is proposed to utilize flat rectangular strips or ars desi ated in Fig. 1 as A and A which are first nt transversely into the semi-circular cross-sectional formation indicated at B and B in Fig. 2.

\ In accordance with the next step of the method the transversely curved sections B and B are then bent or curved longitudinally into the form shown at C and C in Fig. 3.

That is to say, after the flat rectangular strips or bars have been curved transversely, one of them, for example, G, is bent to the proper radius to form the outside of the pipe and the member C is bent on the proper radius in the direction of its longitudinal axis to form I the inside member of the hollow tubular section. As will be observed from Figs. 2 and 3 the side edgeportion of the two sections are preferably bevelled .in opposite directions as indicated at w and 17 to provide a channel 3/ so (Figvs, 4 and 5) to receive welding material Thus, when the parts are assembled as shown in Fig. 4 and welded together by an of the well known welding methods the ho ow tubular section of Fig. 5 is provided.

, Clearly sections of any length or radius. may be made as will be apparent from Figs.

6, 7 and 8 of the drawings.

While the drawings illustrate one form of procedure in carrying out the method, never- V theless, it will be understood that-the flat rectangular strip A may be provided with its transverse curvature and then the said strip A cut into lengths such as B and B for example,

according to whether the length of material I is necessary for the inside or outside radius of the elbow. That is to say, the flat rectangular strip may be rolled in len hs into its trans- Figure 4 1s a view of the completely formed forming lengths after which the latter lengths versely curved form and t en cut into elbow 2 a v 1,a4o,om

ma be bent longitudinally to the desired ra 1us.

' Without further description it is thought that the features and advantages of the 1n- 6 vention will be readily apparent to those skilled in the art, and it Will of course be understood that changes in the form, proportion and minor details of construction may be resorted to, without departing from 10 the spirit of the invention and scope of the I appended claims.

. I claim 1. A method of making hollow curved metallic sections from flat strip stock which con- 15 sists in shaping two metallic blanks first transversely and then longitudinally to a desired radius, assembling said sections with their curved portions facing each other and then connecting the edges of said sections by 2 a welded joint.

2. A method of making hollow curved metallic sectionsfrom fiat strip stock which consists in first subjecting flat rectangular rolled metal strips to a bending operation 25 which shapes them into trough forms, then bending said troughed sections to form the inside and outside of a curved hollow section of the desired radius, and subsequently uniting the meeting edges of said sections to form 3 the completed article.

. 3. A method of making elbows and the like from flat strip stock which consists in bending a flat rectangular strip into transversely curved formation, then cutting the same into 5 sections of the proper length to form complemental elbow forming sections, then bendmg said complemental sections in the direction of their length to the desired radius, and subsequently uniting the meeting edges of l said transversely and longitudinally curved sections by a welding operation.

4. A method of making elbows and the like which consists in preliminarily forming pieces of fiat strip stock material transversely 4 into troughed formation, bending said pieces of material longitudinally according to the desired radius of vthe elbow, then assembling the formed and bent pieces whereby the meetin edges occur at the sides of the elbow,

Method of forming a windage cover for a gas turbine engine the method including forming a continuous ring from a sheet of metal and bending and cutting the continuous ring to form at least two arcuate segments